"You are eating cookies."
1) jesz / jecie is both ok singular vs plural you
2) cookies is plural - plural ciasteczko is ciasteczka, Biernik (accusative) ciasteczka is ciasteczka
3) if you wanted to say
Thou eat cookie - jesz ciasteczko
yes. all neuter nouns have accusative=nominative and all -o ending (in nominative) nouns are neuter.
Not all -o ending nouns are neuter (dziadzio - diminutive of grandpa; Mieszko - polish king). There are very rare though.
you are right of course. I should have said most. I'd add "tato" which is a variant of a "dad" that I use.
It says "ciastka"... is that just my app messing up or is it another way to say cookies? :)
In my opinion - even better way, I think 'ciasteczka' is needlessly diminutive (although 'ciastko' may be a bit ambiguous). But someone in the beginnings of this course went with "ciasteczka" and it stayed.
For some reason, no matter what answer you're going for, is wrong. I don't know why it is so?
Usually when people write about such problems, it's because they had 'check all the correct answers' exercise and they didn't notice that there is more than one correct answer.
As English 'you' is both 2nd person singular and 2nd person plural, in 99% of the sentences with 'you', both singular and plural will be equally probable answers. So here, either "jesz" (singular) or "jecie" (plural).
"Pijesz wodę" (You [drink/are drinking] water) uses singular 'you'; "Jecie ciasteczka" (You [eat/are eating] cookies) uses plural 'you'.
"You are eating cookies - Wy jesz ciasteczka" is matched to incorrect translation, it's shown that "ty" is applicable for this case.
I'm not sure what you mean. The acceptable answers are "(Ty) jesz ciastka/ciasteczka" and "(Wy) jecie ciastka/ciasteczka", so singular 'you' and plural 'you'. "Wy jesz" mixes plural pronoun with singular form of the verb.